Absorption spectra of peroxyacyl nitrates (nPANs) at room temperature (298 +/- 3 K) have been measured in the mid-infrared range (700-2050 cm (1)) using an environmental chamber/FTIR absorption system. nPANs are generated in situ as main products in the NO3 radical reactions with aldehydes. Both peak absorption cross-sections and integrated band intensities for the principal absorption bands in the peroxypropionyl nitrate (PPN), peroxy-n-butyryl nitrate (PnBN), peroxy-n-valeryl nitrate (PnVN), peroxyacryloyl nitrate (APAN) and peroxycrotonyl nitrate (CPAN) spectra have been derived from quantitative laboratory measurements. Results are compared with literature data when available and in those cases, a good agreement is observed. (C) 2008 Elsevier B.V. All rights reserved.